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>>--> 12-02-98  08:12  S.SHEPPARD     (SHS)    ADSM and Virtual Tap
>>--> 12-02-98  08:12  S.SHEPPARD     (SHS)    ADSM and Virtual Tap

When we acquired our 3494, one of the options was to go with the VTS.
After a little examination and input from IBM, it was determined that
since high ADSM and DFSMShsm tape activity was the problem we were
trying to solve, the VTS was not a good idea. Main reason was because
of ADSM reclaims and HSM recycles in conflict with theequivalent
activity in the VTS itself.  If the goal is to fill 3590 tapes and get
automation, then both ADSM and HSM will do a pretty good job of the
first and the 3494 (without VTS) will handle the second.
Sam Sheppard
San Diego Data Processing Corp.
shs AT sddpc.sannet DOT gov
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>>--> 12-02-98  07:55  ..NETMAIL     ()     ADSM and Virtual Tap
>>--> 12-02-98  07:55  ..NETMAIL     ()     ADSM and Virtual Tap
>Date:         Wed, 2 Dec 1998 10:23:56 -0500
>Reply-To:     "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
>From:         Thomas Denier <Thomas.Denier AT MAIL.TJU DOT EDU>
>Subject:      ADSM and Virtual Tape Server
>_________________________________Top_of_Message________________________________
>
>My site is planning to install an ADSM Version 3 server on an MVS system. We
>are also planning to install a 3494 automatic tape library with a VTS (Virtual
>Tape Server). Current plans call for sending incoming backup data to primary
>tape storage pools using the VTS. The disk cache on the VTS is almost
>certainly large enough to keep new backup data on disk until a COPY STGPOOL is
>done to produce off-site backups, and probably large enough to keep partially
>filled virtual tapes on disk until ADSM puts more data on them.
>
>I am a bit nervous about the amount of behind the scenes tape activity this
>approach will entail. Each time ADSM adds data to a partially filled virtual
>volume, the real tape space occupied by the old version of the virtual volume
>will go out of use. I would expect this to end up triggering large amounts of
>VTS tape reclamation activity. I am also nervous about the two-tiered
>reclamation we will be doing as ADSM clears virtual volumes and the VTS
>eventually clears the real volumes formerly occupied by the reclaimed virtual
>volumes.
>
>What are the pros and cons of using a VTS for ADSM primary storage pools?
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